This invention relates to an image forming apparatus that forms an image on a sheet-like recording medium.
A conventional image forming apparatus (such as a printer) includes a medium storage unit (i.e. a sheet feed cassette or a sheet feed tray) that stores a recording medium such as a sheet and the like. This apparatus is designed to convey the recording medium stored in the medium storage unit to an image forming position (a position where an image is formed on the recording medium). Specifically, the conventional image forming apparatus includes a supply roller and a conveyance roller. The supply roller supplies the recording medium stored in the medium storage unit into a conveyance path. The conveyance roller conveys the recording medium after performing skew correction by temporarily restricting passage of the recoding medium conveyed by the supply roller in the conveyance path.
There is also a known printer as another type of image forming apparatus. The printer comprises a common motor to drive both a supply roller and a conveyance roller in order to achieve downsizing of the apparatus and cost reduction. In the printer, rotary driving force is transmitted such that while the supply roller is rotated in a forward direction (in a direction where a recording medium is conveyed toward an image forming position), the conveyance roller is rotated in a reverse direction. This configuration allows skew correction by the conveyance roller.
Specifically, the printer includes a first roller and a second roller. The first roller supplies a sheet stored in a sheet feed cassette to a conveyance path, and the second roller passes and further conveys the sheet conveyed by the first roller.
Also, the printer includes a feed roller, as a conveyance roller, that passes and further conveys the sheet conveyed by the second roller after performing skew correction. The feed roller is rotated in the reverse direction while both the first roller and the second roller are rotated in the forward direction to convey the sheet. When a leading end of the sheet conveyed by the second roller is pressed by the feed roller, a rotating direction of the motor is reversed. Thereby, the sheet conveyed by the second roller is conveyed after the feed roller performs skew correction.
When the sheet is conveyed to the second roller, a rotating shaft of the first roller is moved upward separating away from a surface of a sheet stored in the sheet feed cassette. Moreover, the second roller is configured so as to be stopped rotating and remain in a free state when the rotating direction of the motor is reversed. Accordingly, the first roller and the second roller do not interrupt conveyance of the sheet by the feed roller even when the rotating direction of the motor is reversed.